Species 45 (34 in the flora): temperate and arctic/alpine regions, North America, Mexico, South America, Eurasia.

Some species of Antennaria, especially the stoloniferous, mat-forming species, are cultivated as rock-garden ornamentals. Among the more suitable species widely used for that purpose are A. dioica, A. microphylla, A. parvifolia, A. rosea, and A. suffrutescens. Clones with red or pink phyllaries have been selected as prized for cultivation. Some species are used in the dried-flower trade. Phylogenetic relationships within Antennaria. Antennaria is composed of two major lineages: the Leontipes group, mostly restricted to western North America, and the Catipes group, occurring throughout the Northern Hemisphere and South America (R. J. Bayer et al. 1996). The Leontipes group consists of five smaller groups (the Geyerae, Arcuatae, Argenteae, Dimorphae, and Pulcherrimae) and comprises species that are primarily diploid (tetraploids are known only in A. dimorpha and A. pulcherrima, Bayer and G. L. Stebbins 1987, and, as far as is known, always amphimictic, sexually reproducing). Most of the species of the Leontipes group lack horizontal stoloniferous growth (except A. flagellaris and A. arcuata). Morphologically, the Leontipes group is considered primitive in the genus, based on unspecialized morphologic features such as non-stoloniferous growth, lack of extensive polyploidy, and general lack of well-developed sexual dimorphism; the Catipes group has amphimictic diploids and tetraploids. Derived from them are all of the polyploid agamic complexes (fig. 1). Most species of the Catipes group have horizontal stolons, an effective means of asexual reproduction; it is considered more specialized than the Leontipes group. For the most part, the smaller monophyletic groups composing the Leontipes group correspond to traditionally recognized groups (R. J. Bayer 1990; Bayer et al. 1996). The Geyerae group is monotypic, consisting of Antennariageyeri, and the tendency toward polygamodioecy in that species, along with its lack of basal leaves, makes it more similar morphologically to Anaphalis than to the remainder of Antennaria. Antennaria arcuata is the only member of the newly recognized Arcuatae group, and it was previously considered to be a portion of the Argenteae along with A. luzuloides and A. argentea (Bayer), a relationship that was always considered weak. The Argenteae group comprises A. argentea, A. luzuloides, and A. stenophylla and is sister to the A. arcuata–A. geyeri clade (Bayer et al.). The Dimorphae group, A. dimorpha and A. flagellaris, is sister to the Geyerae-Arcuatae-Argenteae clade (Bayer et al.), and the Pulcherrimae group comprises A. pulcherrima, A. anaphaloides, and A. lanata (Bayer; Bayer et al.). The Catipes group is well supported in both morphologic and molecular phylogenetic trees (R. J. Bayer et al. 1996); support for subclades within Catipes is weak. Traditionally, members of Catipes were split into the Alpinae, distributed in tundra, with black or olivaceous phyllaries, and the Dioicae with lighter phyllaries. Based on DNA sequence data and morphology, the two groups are artificial and should be abandoned (Bayer et al.). Amphimixis, apomixis (agamospermy), and high levels of polyploidy (Bayer and T. M. Minish 1993) are prevalent among polyploid derivatives of the Catipes group, which consists of diploids and some tetraploids in which sexual dimorphism is highly evolved (Bayer 1990). Some species of the Catipes group are specialized as edaphic endemics, e.g., Antennaria virginica on Devonian-age shale barrens (Bayer and G. L. Stebbins 1987, 1993), A. suffrutescens on serpentine (Bayer and Stebbins 1993), and A. aromatica and A. densifolia on limestone talus (Bayer 1989). Five polyploid agamic complexes, A. alpina (together with the smaller A. media, A. monocephala, and A. friesiana complexes), A. howellii, A. parlinii, A. parvifolia, and A. rosea, have evolved via multiple hybridization among members of the Catipes group (Bayer 1987, 1997). The great success of the Catipes group seems to be correlated with their ability to grow in diverse habitats throughout their range across Eurasia and North America to Tierra del Fuego in South America, and to their acquisition of characteristics such as strong sexual dimorphism, polyploidy, agamospermy, and vegetative reproduction (stolons). The amphimictic taxa of the Catipes group include A. aromatica, A. corymbosa, A. densifolia, A. dioica, A. friesiana subsp. alaskana, A. friesiana subsp. neoalaskana, A. marginata, A. microphylla, A. monocephala subsp. monocephala, A. neglecta, A. plantaginifolia, A. pulchella, A. racemosa, A. rosulata, A. solitaria, A. suffrutescens, A. umbrinella, and A. virginica. Some of those have contributed to the genetic makeup of the polyploid complexes, whose morphologic variation is correlated to the number of diploid genomes contributed to the origin of the complex. Morphologic overlap between the complexes is a direct consequence of pivotal genomes recurring in some complexes. For example, the A. parlinii and A. howellii complexes share two pivotal genomes from A. plantaginifolia (PLA) and A. racemosa (RAC). Some apomictic clones (identified under the name A. howellii subsp. howellii in part) appear to bridge the morphologic gap between the two complexes. The A. parlinii complex has three diploid progenitors: A. solitaria (SOL), A. plantaginifolia (PLA), and A.racemosa (RAC); the A. howellii complex has five: A. marginata (MAR), A. neglecta (NEG), A. plantaginifolia (PLA), A. racemosa (RAC), and A. virginica (VIR). Antennaria parvifolia has three major progenitors: A.dioica (DIO), A. neglecta (NEG), and A. marginata (MAR); it is likely that high elevation segregates of the complex also contain genomic contributions from A. pulchella (PUL) and/or A. media. Antennaria rosea is morphologically the most diverse of the polyploid complexes and has as its primary progenitors: A. aromatica (ARO), A. corymbosa (COR), A. microphylla (MIC), A. racemosa (RAC), and A. umbrinella (UMB). It is likely that A. marginata (MAR), A. rosulata (ROS), and possibly A. suffrutescens (SUF) have also contributed to the origins of some A. rosea clones. The circumpolar allopolyploid A. alpina complex appears to have its origins from the amphimictic, dark-phyllaried, arctic-alpine taxa including A. aromatica (ARO), A. densifolia (DEN), A. friesiana subsp. alaskana (ALA), A. friesiana subsp. neoalaskana (NEO), A. monocephala subsp. monocephala (MON), and A. pulchella (PUL). Three polyploid complexes, A. friesiana subsp. friesiana, A. media, and A. monocephala subsp. angustata (ANG) appear to be of non-hybrid, autopolyploid origin and are direct polyploid derivatives of A. friesiana (subspp. alaskana and neoalaskana), A. monocephala subsp. monocephala, and A. pulchella, respectively; most polyploids are of multiple hybrid origin from among multiple amphimicts. Antennaria marginata has also given rise to apparent autopolyploid apomictic derivatives. Key pivotal genomes involved in the origins of the polyploid complexes include Antennaria aromatica, A. marginata, A. neglecta, A plantaginifolia, A. pulchella, and A. racemosa; significant contributions have also been made by A. corymbosa, A. densifolia, A. dioica, A. friesiana, A. microphylla, A. monocephala, A. solitaria, A. umbrinella, and A. virginica.Classification of Antennaria. Past practice has been to attempt to recognize each agamospecies as a distinct taxonomic entity, usually at species rank. That has led to unwieldy classifications that can be used only by experts on the group. Clearly, that method is unsatisfactory and a more reasonable scheme for classifying polyploid agamic complexes, such as the one advocated by E. Babcock and G. L. Stebbins (1938), should be adopted. R. J. Bayer and Stebbins (1982) were the first to use the Babcock and Stebbins method in Antennaria. Because the sexual diploids are morphologically discrete, they are each recognized as species. Polyploids that are morphologically identical with sexual diploid (nonhybrid- or auto-polyploid) taxa, whether they are agamospermous or amphimictic, are treated as conspecific with their sexual diploids, e.g., tetraploid cytotypes of Antennariavirginica and some other taxa are treated as conspecific with their corresponding sexual diploids because they are morphologically (R. J. Bayer and G. L. Stebbins 1982) and, in the case of A. virginica, genetically (Bayer and D. J. Crawford 1986) inseparable from the sexual diploids. Sexual and asexual polyploids that are of hybrid origin (segmental and genomic allopolyploids) are recognized as species because their genetic composition is not attributable to any single diploid origin. For example, Bayer and Stebbins classified A. parlinii as distinct from its sexual diploid progenitors, A. plantaginifolia, A. racemosa, and A. solitaria. A. Cronquist (1945) recognized A. parlinii (sensu Bayer and Stebbins) as two varieties of A. plantaginifolia, a view Stebbins and I opposed because the polyploids, while containing genes from A. plantaginifolia in their genetic background, also have genes from A. racemosa and A. solitaria (Bayer 1985b; Bayer and Crawford). The polyploid complexes are each defined primarily by assessing their genomic composition through the use of genetic markers, as well as through morphologic studies. This philosophy and method of classification has been extended to the other polyploid agamic complexes. Identifying Antennaria specimens. Users of this treatment should be aware that multiple details must be kept in mind when collecting and trying to identify species of Antennaria. For example, assigning specimens to species in the "mat-forming," stoloniferous Catipes group is particularly difficult because of widespread polyploidy and apomixis. One determinative taxonomic character (whether populations are gynoecious or dioecious) may not be readily observed on herbarium specimens but is readily determined in the field by gender ratios. On herbarium specimens, assuming pistillates are always present in populations, absence of staminates could mean either that they were not collected or that they were actually absent from the population. This character comes into use in separating the infraspecific taxa within both A. monocephala and A.friesiana. If this character cannot be readily determined on herbarium material, i.e., when staminates are absent, then such specimens are best keyed to the specific level only. Another feature of importance in identifying specimens of Antennaria is the presence or absence of well-developed stolons that root at their tips. Some Antennaria species produce stiff, semi-erect stolons that do not root at the tips, and those stolons should not be confused with the typical stolons that are more elongate and horizontal and root at their tips. The final feature of importance in identifying specimens of Antennaria is the presence or absence of flags on tips of mid and distal cauline leaves. Flags are flat, linear, scarious appendages of the leaf tips that are similar to the tips of the phyllaries; they are not to be confused with ordinary subulate or blunt leaf tips that are essentially green and herbaceous. In keys and descriptions, leaves are referred to as flagged or not flagged.